I posted this in the Michigan Mashers section and Revvy suggested I post it over here too. I will post it in the Beginners' section as it may be a lower cost way to get into all-grain brewing for those of you presently using extract.

I recently scored some great garage sale finds and needed to give them a workout, so I tested them with a couple of experiments. I tried the Australian method of Brew In A Bag (BIAB) and also did a wet hopping.

Some of the advantages of BIAB are:
Low equipment cost -- only one kettle and a bag
Shorter brew time -- no sparge
Less to clean up

Some of the disadvantages:
Efficiency loss without sparge (somewhat offset by use of a finer crush, mash out, and long drain and squeeze of bag)
Effectively limited to 5-gallon batches
High liquid to grist ratio -- not appropriate for some recipes
Step mash becomes more of a ramp mash

So finer crush of grains is necessity? Why only 5 gallon batch. I saw some one on the net make a 6-6.5 gallon batch.

A finer crush isn't necessary.....as long as you are willing to accept a lower efficiency. Traditional mash tuns have a limit to how fine of material they can have without it clogging up the screen. You may see references to a stuck sparge. With that limit the water can't get to the middle of the larger particles so they don't fully convert and their efficiency suffers for that. BIAB has a tremendous filter area comparatively so the stuck sparge isn't a problem (most don't even sparge because they can squeeze the wort out) thus allowing a finer particle which gets higher efficiency. There isn't a theoretical limit on the size of batch you can make; in fact some are doing 10 gallon batches but at some point you have to lift the bag of grains and it gets pretty heavy. The practical limit is when you are trying to lift the bag of grain to let it drain and the seam rips open, dropping your grain back into the kettle.